FIELD OF THE INVENTION
This invention relates to an automatic rim replacing mechanism capable of replacing upper and lower rims on a tire uniformity inspecting machine in a full automatic fashion, for example, at the time of changing the tire size. The rim replacing mechanism is also capable of mounting upper and lower rims corresponding to a desired tire size selectively from a number of rim assemblies of different sizes provided on a carriage or indexing table.
As well known in the art, upper and lower rims are mounted on upper and lower spindles of the tire uniformity machine by bolts or similar clamp means. A tire is held in position by the upper and lower rims during the uniformity operation, including introduction of compressed air into the tire, rotation of the tire through the upper spindle, application of load on the tire, etc. Since the rims are required to be in conformity with the tire in dimensions, a change of the tire size immediately necessitates replacement of the rims on the upper and lower spindles by rims of corresponding dimensions. This sort of inspecting machines need extremely high precision and are very expensive, so that it is uneconomical to use them exclusively for tires of a particular kind or of a particular size. Namely, it is advantageous to make the machine adaptable to as many tire sizes as possible. According to conventional procedures, the replacement of upper and lower rims usually requires a long time and a meticulous skill to set the rims in the respective positions with a high degree of accuracy. In addition, the rim replacement compels very severe working conditions since rims of relatively large weights have to be handled in a narrow restricted space all by manual labor. Therefore, the current tire uniformity machines are mostly used as a machine for a specific tire size or for tires of a restricted range in size, for the purpose of reducing the frequency of rim replacement. However, from the standpoint of operational efficiency and productivity, it is desirable to broaden the restricted range as much as possible to cope with a wider range of tire sizes. The first technical problem to be solved for this purpose is automation of the rim replacing operation for a variety of tire sizes.